1. Field
The invention is in the field of fabricated filter cloths for installation on chamber type filter presses prior to passing a solids-containing liquid therethrough to remove the solids from the liquid. Such filter cloths are commonly called "duplex" filter cloths.
2. State of the Art
Duplex filter cloths in the form of double pieces of sheet filter cloth material with interconnecting collar about the circumferential margins of the filtrate-feed openings of the two otherwise separate pieces are well known and widely used in chamber type filter presses.
The individual filter cloth pieces are conventionally fabricated from felted filter cloth material by cutting flat sheets, usually of equal size, from the sheet filter cloth material, inturning inner margins bordering the respective filtrate-feed openings thereof, and sewing such inturned margins to corresponding circular margins of a separate collar, usually made of a strong material such as a length of a coarsely woven fabric tape. Fabricated in this way, however, the so-called "barrel neck" collar joining the two filter cloth pieces together around their filtrate-feed openings do not fit snugly and smoothly against the supporting structure of the filter press in which they are installed.